Field of the Invention
The invention relates to an inking unit in a printing machine, more particularly, having a throw-off device for throwing an ink applicator roller group off a plate cylinder.
The published German Patent Document DE 37 103 00 A1 describes a switching device for inking unit rollers in printing machines, wherein, by actuating an operating cylinder, two intermediate rollers can be lifted off distributor cylinders, so that ink flow continues only via the two first applicator rollers. In this switching state of the inking unit, two strands or ribbons of ink are provided with the task of continuing to even out the ink applied by the two first applicator rollers. Although, in the aforenoted switching state, no ink flow takes place over the applicator rollers associated with the two strands or ribbons of ink, these applicator rollers and, consequently, all of the applicator rollers, are also thrown onto the plate cylinder. An applicator roller throw-off cam is pivotable as a result of the actuation of another operating cylinder, so that all the applicator rollers can be thrown off the plate cylinder.
A disadvantage of the aforedescribed switching device is that the inking unit reacts sluggishly to changes in the inking, because a predetermined volume of ink is always stored in the two strands or ribbons of ink used to even out the applied ink, and this volume only very slowly equalizes any corrections that are necessary and, as a result of this sluggishness, is the cause of paper wastage. In addition, the inking unit also requires a comparatively great amount of time for being set to the respective printing jobs.
The published German Patent Document DE 42 30 090 C2 describes an inking unit for printing machines that is operatable as a so-called short or anilox inking unit, in that the printing plate is inked only via a first ink applicator roller group, and a second ink applicator roll group is lifted off the plate cylinder by a throw-off device. With respect to this inking unit, Although the deficiencies associated with the switching device described hereinbefore in the published German Patent Document DE 37 103 00 A1 are no longer present in that of the published German Patent Document DE 42 30 090 C2, the latter does not describe any specific throw-off device that is suitable for lifting off or disengaging the second ink applicator roller group.
It is accordingly an object of the invention to provide an inking unit for printing machines that is operatable in a variable manner and, in particular, in the short or anilox inking unit mode of operation, and that has ink applicator rollers which can be thrown off a plate cylinder by a throw-off device having a relatively simple construction and being very reliable functionally.
With the foregoing and other objects in view, there is provided, in accordance with the invention, an inking unit in a printing machine, comprising a throw-off device for throwing an ink applicator roller group off a printing form cylinder, the throw-off device including a rotatable roller throw-off cam contoured so that, in a first rotational position of the cam, all the ink applicator rollers are in contact with the form cylinder and, in a second rotational position of the cam, the ink applicator roller group is thrown off the form cylinder and at least one ink applicator roller is in contact with the form cylinder.
In accordance with another feature of the invention, in the second rotational position of the cam, a first ink applicator roller group is thrown off the form cylinder, and a second ink applicator roller group is in contact with the form cylinder.
In accordance with a further feature of the invention, in the second rotational position of the cam, as viewed in a direction of rotation of the cylinder, a first ink applicator roller and a second ink applicator roller are in contact with the form cylinder.
In accordance with an added feature of the invention, in the second rotational position of the cam, as viewed in a direction of rotation of the cylinder, a third ink applicator roller and a fourth ink applicator roller of four ink applicator rollers are in contact with the form cylinder.
In accordance with an additional feature of the invention, in a third rotational position of the cam, all the ink applicator rollers are thrown off the form cylinder.
In accordance with yet another feature of the invention, in a fourth rotational position of the cam, as viewed in a direction of rotation of the cylinder, the first ink applicator roller and the second ink applicator roller are in contact with the form cylinder.
In accordance with yet a further feature of the invention, in the second rotational position of the cam, as viewed in a direction of rotation of the cylinder, the first ink applicator roller is in contact with the form cylinder and the second, and a third and a fourth ink applicator roller are thrown off the form cylinder.
In accordance with yet an added feature of the invention, the inking unit includes two operating cylinders to which pressurized fluid is applicable for rotating the roller throw-off cam into rotational positions of the cam.
In accordance with yet an additional feature of the invention, the operating cylinders are formed as one structural unit having a tandem cylinder.
In accordance with still another feature of the invention, the roller throw-off cam has two guide tracks disposed side by side.
In accordance with still a further feature of the invention, the roller throw-off cam is rotatably mounted coaxially with the form cylinder.
In accordance with still an added feature of the invention, the roller throw-off cam is revolvingly rotatable and driven.

In accordance with still an additional feature of the invention, the roller throw-off cam is contoured approximately as shown in FIGS. 2 to 5, on the one hand, and FIGS. 7 to 13, on the other hand, respectively.
In accordance with a concomitant aspect of the invention, there is provided a printing machine, especially a rotatable offset printing machine, having at least one inking unit constructed with at least one of the foregoing features.
Thus, the inking unit according to the invention in a printing machine, having a throw-off device for throwing an ink applicator roller group off a form or plate cylinder, is distinguished by the fact that the throw-off device is a rotatable roller throw-off cam that is contoured so that, in a first rotational position of the cam, all the ink applicator rollers are in contact with the form or plate cylinder and, in a second rotational position of the cam, the ink applicator roller group is thrown off the form or plate cylinder, and at least one ink applicator roller is in contact with the form or plate cylinder.
There are offset printing machines in which the inking unit and a dampening unit can be coupled to one another via a connecting roller, and a dampening solution applicator roller applies an ink/dampening solution mixture to the form or plate cylinder when they are coupled. Such a dampening solution applicator roller is not an ink applicator roller in the sense of the invention. Instead, according to the invention, ink applicator rollers are understood to be those applicator rollers which primarily apply printing ink to the form or plate cylinder.
An advantageous feature of the inking unit according to the invention is that the ink applicator rollers are forcibly controlled by the roller throw-off cam, the ink applicator rollers being located in the respectively required position relative to one another, in each of the rotational positions of the cam, and malfunctioning being virtually impossible. A further advantage is to be seen in the low constructional outlay for the inking unit, which has been achieved as a result of the fact that all the ink applicator rollers have a common roller throw-off cam assigned thereto.
When the roller throw-off cam is in the first rotational position of the cam, both the at least one ink applicator roller and the ink applicator roller group are jointly in contact with the form or plate cylinder in order to ink the cylinder. This corresponds to the normal inking unit mode of operation of the inking unit. The inking unit can be operated as a short or anilox inking unit when the roller throw-off cam is in the second rotational position of the cam, and the form or plate cylinder is inked only by the at least one ink applicator roller.
A first embodiment developing the inking unit according to the invention advantageously is distinguished by the fact that the inking unit comprises at least four ink applicator rollers and, in the short or anilox inking unit mode of operation, corresponding to the second rotational position of the cam, at least two ink applicator rollers are in contact with the form or plate cylinder in order to ink the cylinder.
The invention, however, also includes inking units with altogether only three ink applicator rollers, wherein, in the short or anilox inking unit mode of operation, one ink applicator roller or two ink applicator rollers are in contact with the form or plate cylinder.
A second embodiment for developing the invention or the first embodiment thereof is distinguished by the fact that, in the second rotational position of the cam, as viewed in the direction of rotation of the cylinder, the last and the penultimate ink applicator rollers are thrown off the plate cylinder.
In an inking unit having a total of four serially-arranged ink applicator rollers, the last ink applicator roller corresponds to the fourth ink applicator roller, and the penultimate ink applicator roller corresponds to the third ink applicator roller. In an inking unit having a total of three ink applicator rollers, the last ink applicator roll corresponds to the third ink applicator roller and the penultimate ink applicator roll corresponds to the second ink applicator roller.
The designations of the ink applicator rollers as first, second, third and fourth ink applicator rollers used herein refer to the direction of rotation of the cylinder. Accordingly, the first ink applicator roller is that ink applicator roller which, in the normal inking unit mode of operation, initially inks a specific circumferential printing image point on the form or plate cylinder during each revolution of the cylinder as the first of all the ink applicator rollers and which, for example, is arranged immediately downline, as viewed in the direction of rotation of the cylinder, of a dampening solution applicator roller that dampens the cylinder during the process. Accordingly, the last ink applicator roller is that ink applicator roller which inks the printing image point as the last ink applicator roller before the printing image is transferred from the form or plate cylinder to the printing material or, in an offset printing unit, to a blanket cylinder.
A third embodiment for developing the invention, or for developing the first or second embodiment, is distinguished by the fact that in the second rotational position of the cam, the first ink applicator roller and the second ink applicator roller are thrown off the form or plate cylinder.
In the third embodiment, the second rotational position of the cam is not used to implement the short or anilox inking unit mode of operation, but the first stage of throwing off the four ink applicator rollers from the form or plate cylinder in two stages and, respectively, in pairs.
A further embodiment is distinguished by the fact that a third rotational position of the cam corresponds to a xe2x80x9cprinting offxe2x80x9d position, i.e., a position wherein all the ink applicator rollers are located at a spaced distance from the plate cylinder.
In a development of a second embodiment according to the foregoing further embodiment, it is possible, for example, as a result of the rotation of the roller throw-off cam from the second rotational position of the cam into the third rotational position of the cam, for the first ink applicator roller and the second ink applicator roller to be lifted off the form or plate cylinder. In a development of a third embodiment according to the foregoing further embodiment, it is possible, as a result of the rotation of the roller throw-off cam from the second rotational position of the cam into the third rotational position of the cam, for the third applicator roller and the fourth ink applicator roller to lifted off the form or plate cylinder.
A further embodiment is distinguished by the fact that a fourth rotational position of the cam corresponds to a first stage of throwing the four ink applicator rollers onto the form or plate cylinder in stages, the ink applicator rollers, respectively, being thrown onto the form or plate cylinder in pairs.
In the second embodiment, wherein the second rotational position of the cam serves to implement a first throw-off stage of the ink applicator rollers, the fourth rotational position of the cam can serve to implement the short or anilox inking unit mode of operation.
A further embodiment is distinguished by the fact that, in an inking unit having a total of four ink applicator rollers, in the second rotational position of the cam, only the first ink applicator roller is in contact with the form or plate cylinder.
In this way, a short or anilox inking unit mode of operation can be implemented with only a single ink applicator roller inking the form or plate cylinder in this mode of operation. The second, third and fourth ink applicator rollers can be lifted off the form or plate cylinder as a group of three due to the adjustment of the roller throw-off cam from the first rotational position of the cam into the second rotational position of the cam. As a result of the rotation of the roller throw-off cam from the second rotational position of the cam into the third rotational position of the cam, the first ink applicator roller can also be lifted off the form or plate cylinder, following the group of three, so that all the ink applicator rollers are out of contact with the form or plate cylinder.
A further embodiment is distinguished by the fact that the roller throw-off cam can be adjusted into the rotational positions of the cam by two piston/cylinder units which can be acted upon pneumatically or hydraulically.
The two piston/cylinder units are couplable to one another in such a way that the roller throw-off cam can be adjusted sequentially, in three setting steps, from the first into the second, from the second into the third and from the third into the fourth rotational position of the cam. A first unit of the piston/cylinder units includes a first cylinder housing and a first piston which is displaceable in the housing. A second unit of the piston/cylinder units includes a second cylinder housing and a second piston displaceable in the second housing. For example, the piston/cylinder units are couplable to one another by having the first piston and the second piston permanently or firmly connected to one another, and by permitting the cylinder housings to be moved independently of one another in relation to the connected pistons by the internal application of pressure. In an alternative coupling variation, the first piston can be permanently or firmly connected to the second cylinder housing, the first cylinder housing and the second piston being capable of being moved independently of one another in relation to the connected parts by the application of pressure. It is preferable, according to a further alternative coupling variant, for the first cylinder housing and the second cylinder housing to be permanently connected to one another, so that when pressure is applied, the first piston and the second piston are able to be moved independently of one another in relation to the connected cylinder housings. In all the three varying embodiments of the coupling which are described, the piston/cylinder units are preferably arranged in series so that they align in the axial direction thereof.
A further embodiment is distinguished by the fact that a tandem cylinder to which pressurized fluid can be applied in stages is constructed as a cam setting drive.
The tandem cylinder corresponds to a modification of the third-mentioned coupling variant, the two piston/cylinder units forming one structural unit with two expansion chambers separated from one another. One of the pistons is mounted so that it is displaceable in each of the expansion chambers, it being possible for the pistons to be extended from the structural unit in opposite directions by applying pressure to the two expansion chambers. The tandem cylinder is a particularly space-saving cam setting drive, which can be installed in the smallest space between other machine parts.
A further embodiment is distinguished by the fact that the roller throw-off cam, as viewed in the axial direction thereof, has two cam planes which are located one behind another and are contoured differently from one another.
Each of the cam planes can be formed, for example, by a cam disk having at least one circumferential lifting cam for lifting the inking rollers. The cam disks can be firmly or permanently connected to one another, for example, by being screwed together. The two cam disks can intrinsically be constructed identically, the different cam contour in the axial direction of the cam disks resulting from the fact that the cam disks are connected to one another in a position wherein they are rotated in the circumferential direction in relation to one another, for example, through 180xc2x0. A solid construction of the roller throw-off cam having the two cam planes, for example in a casting process with subsequent machining to remove material, is also possible. A first one of the cam planes can then serve to throw a first ink applicator roller or a first ink applicator roller group on and off, and a second of the cam planes can serve to throw a second ink applicator roller or a second ink applicator roller group on and off.
A further embodiment is distinguished by the fact that an axis of rotation of the cam extends coaxially with the axis of the form or plate cylinder.
The scope of the invention, however, also includes inking units wherein the roller throw-off cam is rotatably mounted so as to be offset eccentrically with respect to the axis of rotation of the form or plate cylinder, and has a cam axis of rotation extending parallel to the axis of rotation of the form or plate cylinder.
A further embodiment is distinguished by the fact that the roller throw-off cam is rotatable through more than 3600 about the axis of rotation thereof and, in the process, can be set into the corresponding rotational positions of the cam.
By rotating the roller throw-off cam exclusively in a single direction of rotation, for example, in the clockwise direction, the roller throw-off cam can be rotated in successive setting steps from an initial position, which can, for example, correspond to the first rotational position of the cam, into an end position, which for example can correspond to the fourth rotational position of the cam, and by being rotated farther while maintaining the direction of rotation, can be rotated out of the end position and into the initial position again. In this way, the roller throw-off cam can be rotated from the first into the second, from the second into the third, from the third into the fourth and from the fourth into the first rotational position of the cam again in the aforementioned sequence.
The inking unit is particularly suitable for a rotary printing machine which, for example, can be constructed as an offset printing machine.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an inking unit in a printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: